Ford Mustang Service Manual: Index Card

Noise is any undesirable sound, usually unpleasant in nature. Vibration is
any motion, shaking or
trembling, that can be felt or seen when an object moves back and forth or up
and down. Harshness is
a ride quality issue where the vehicle's response to the road transmits sharply
to the customer.

Harshness normally describes a firmer than usual response from the suspension
system. Noise,
vibration and harshness (NVH) is a term used to describe these conditions, which
result in varying
degrees of dissatisfaction. Although, a certain level of NVH caused by road and
environmental
conditions is normal. This section is designed to aid in the diagnosis, testing
and repair of NVH
concerns.

Acceptable Noise, Vibration and Harshness

All internal combustion engines and drivelines produce some noise and
vibration; operating in a real
world environment adds noise that is not subject to control. Vibration
isolators, mufflers and dampers
reduce these to acceptable levels. A driver who is unfamiliar with a vehicle can
think that some sounds
are abnormal when actually the sounds are normal for the vehicle type. For
example, Traction-Lok
differentials produce a slight noise on slow turns after extended highway
driving. This is acceptable
and has no detrimental effect on the locking axle function. As a technician, it
is very important to be
familiar with vehicle features and know how they relate to NVH concerns and
their diagnosis. For
example, if the vehicle has automatic overdrive, it is important to test drive
the vehicle both in and out
of overdrive mode.

Diagnostic Theory

The shortest route to an accurate diagnosis results from:

system knowledge, including comparison with a known good system.

system history, including repair history and usage patterns.

condition history, especially any relationship to repairs or sudden
change.

knowledge of possible sources.

using a systematic diagnostic method that divides the system into
related areas.

The diagnosis and correction of noise, vibration and harshness concerns
requires:

a road or system test to determine the exact nature of the concern.

an analysis of the possible causes.

testing to verify the cause.

repairing any concerns found.

a road test or system test to make sure the concern has been corrected
or brought back to
within an acceptable range.

Glossary of Terms

Acceleration-Light

An increase in speed at less than half throttle.

Acceleration-Medium

An increase in speed at half to nearly full throttle, such as 0-97 km/h (0-60
mph) in approximately 30
seconds.

Acceleration-Heavy

An increase in speed at one-half to full throttle, such as 0-97 km/h (0-60
mph) in approximately 20
seconds.

Ambient Temperature

The surrounding or prevailing temperature.

Amplitude

The quantity or amount of energy produced by a vibrating component (G force).
An extreme vibration
has a high amplitude. A mild vibration has a low amplitude.

Backlash

Gear teeth clearance.

Boom

Low frequency or low pitched noise often accompanied by a vibration. Also
refer to Drumming.

When the service brakes are applied with enough force to hold the vehicle
against movement with the
transmission in gear.

Buffet/Buffeting

Strong noise fluctuations (less than 1000 Hz) caused by gusting winds. An
example would be wind
gusts against the side glass.

Buzz

A low-pitched sound like (200-5000 Hz) that from a bee. Often a metallic or
hard plastic humming
sound. Also describes a high frequency (200-800 Hz) vibration. Vibration feels
similar to an electric
razor.

Camber

The angle of the wheel in relation to the true vertical as measured looking
from the front of the vehicle.

Camber is positive when the wheel angle is offset so that the top of the wheel
is positioned away from
the vehicle.

Caster

The angle of the steering knuckle in relation to the true vertical as
measured looking from the side of
the vehicle.

Item

Description

1

Positive caster

2

True vertical

3

Steering axis

Chatter

A pronounced series of rapidly repeating rattling or clicking sounds.

Chirp

A short-duration high-pitched noise associated with a slipping drive belt.

Chuckle

A repetitious low-pitched sound. A loud chuckle is usually described as a
knock.

Click

A sharp, brief, non-resonant sound, similar to actuating a ball point pen.

Clonk

A hydraulic knocking sound. Sound occurs with air pockets in a hydraulic
system. Also described as
hammering.

Clunk/Driveline Clunk

A heavy or dull, short-duration, low-frequency sound. Occurs mostly on a
vehicle that is accelerating or
decelerating abruptly. Also described as a thunk.

Coast/Deceleration

Releasing the accelerator pedal at cruise, allowing the engine to reduce
vehicle speed without
applying the brakes.

Coast/Neutral Coast

Placing the transmission range selector in NEUTRAL (N) or depressing the
clutch pedal while at
cruise.

Constant Velocity (CV) Joint

A joint used to absorb vibrations caused by driving power being transmitted
at an angle.

Controlled Rear Suspension Height

The height at which a designated vehicle element must be when driveline angle
measurements are
made.

Coupling Shaft

The shaft between the transfer case and the front drive axle or, in a
two-piece rear driveshaft, the front
section.

A condition in which an engine's center mass is not concentric to the
rotation center, causing
excessive motion.

Engine Misfire

When combustion in one or more cylinders does not occur or occurs at the
wrong time.

Engine Shake

An exaggerated engine movement or vibration that directly increases in
frequency as the engine speed
increases. It is caused by non-equal distribution of mass in the rotating or
reciprocating components.

Flexible Coupling

A flexible joint.

Float

A drive mode on the dividing line between cruise and coast where the throttle
setting matches the
engine speed with the road speed.

Flutter

Mid to high (100-2000 Hz) intermittent sound due to air flow. Similar to a
flag flapping in the wind.

Frequency

The rate at which a cycle occurs within a given time.

Gravelly Feel

A grinding or growl in a component, similar to the feel experienced when
driving on gravel.

Grind

An abrasive sound, similar to using a grinding wheel, or rubbing sand paper
against wood.

Hiss

Steady high frequency (200-800 Hz) noise. Vacuum leak sound.

Hoot

A steady low frequency tone (50-500 Hz), sounds like blowing over a long neck
bottle.

Howl

A mid-range frequency (200-800 Hz) noise between drumming and whine. Also
described as a hum.

Hum

Mid-frequency (200-800 Hz) steady sound, like a small fan motor. Also
described as a howl.

Hz

Hertz; a frequency measured in cycles per second.

Imbalance

Out of balance; heavier on one side than the other. In a rotating component,
imbalance often causes
vibration.

Inboard

Toward the centerline of the vehicle.

Intensity

The physical quality of sound that relates to the strength of the vibration
(measured in decibels). The
higher the sound's amplitude, the higher the intensity and vice versa.

Isolate

To separate the influence of one component to another.

Knock

A heavy, loud, repetitious sound, like a knock on the door.

Moan

A constant, low-frequency (100-200 Hz) tone. Also described as a hum.

Neutral Engine Run-Up (NERU) Test

The operation of the engine through the normal rpm range with the vehicle
standing still and the
transmission disengaged. This test is used to identify engine related
vibrations.

Neutralize/Normalize

To return to an unstressed position. Used to describe mounts. Refer to Bound
Up.

Outboard

Away from the centerline of the vehicle.

Ping

A short duration, high-frequency sound, which has a slight echo.

Pinion Shaft

The input shaft in a driving axle that is usually a part of the smaller
driving or input hypoid gear of a
ring and pinion gearset.

Pitch

The physical quality of sound that relates to its frequency. Pitch increases
as frequency increases and
vice versa.

Pumping Feel

A slow, pulsing movement.

Radial/Lateral

Radial is in the plane of rotation; lateral is at 90 degrees to the plane of
rotation.

Item

Description

1

Lateral runout

2

Radial runout

Rattle

A random and momentary or short duration noise.

Ring Gear

The large, circular, driven gear in a ring and pinion gearset.

Road Test

The operation of the vehicle under conditions intended to produce the concern
under investigation.

Roughness

A medium-frequency vibration. A slightly higher frequency (20 to 50 Hz) than
a shake. This type of
vibration is usually related to drivetrain components.

Runout

Lateral runout means measuring the movement or "wobble" of a wheel or tire at
the sidewall. Radial
runout means measuring the out-of-round at the tread surface.

Rustling

Intermittent sound of varying frequency (100-2000 Hz), sounds similar to
shuffling through leaves.

Shake

A low-frequency vibration (5-20 Hz), usually with visible component movement.
Usually relates to tires,
wheels, brake drums or brake discs if it is vehicle speed sensitive, or engine
if it is engine speed
sensitive. Also referred to as a shimmy or wobble.

Shimmy

An abnormal vibration or wobbling, felt as a side-to-side motion of the
steering wheel in the driveshaft
rotation. Also described as waddle.

Shudder

A low-frequency vibration that is felt through the steering wheel or seat
during light brake application.

Slap

A resonance from flat surfaces, such as safety belt webbing or door trim
panels.

Slip Yoke/Slip Spline

The driveshaft coupling that allows length changes to occur while the
suspension articulates and while
the driveshaft rotates.

Squeak

A high-pitched transient sound, similar to rubbing fingers against a clean
window.

Squeal

A long-duration, high-pitched noise.

Static Balance

The equal distribution of weight around the wheel. Statically unbalanced
wheel and tire assemblies can
cause a bouncing action called wheel tramp. This condition will eventually cause
uneven tire wear.

Tap

A light, rhythmic, or intermittent hammering sound, similar to tapping a
pencil on a table edge.

The change in tire diameter in the area where the tire contacts the ground.

Tire Flat Spots

A condition commonly caused by letting the vehicle stand while the tires cool
off. This condition can be
corrected by driving the vehicle until the tires are warm. Also, irregular tire
wear patterns in the tire
tread resulting from wheel-locked skids.

Tire Force Vibration

A tire vibration caused by variations in the construction of the tire that is
noticeable when the tire
rotates against the pavement. This condition can be present on perfectly round
tires because of
variations in the inner tire construction. This condition can occur at wheel
rotation frequency or twice
rotation frequency.

Transient

A noise or vibration that is momentary, a short duration.

Two-Plane Balance

Radial and lateral balance.

Vibration

Any motion, shaking or trembling, that can be felt or seen when an object
moves back and forth or up
and down.

Whine

A constant, high-pitched noise. Also described as a screech.

Whistle

High-pitched noise (above 500 Hz) with a very narrow frequency band. Examples
of whistle noises are
a turbocharger or airflow around an antenna.

Noise, Vibration and Harshness (NVH) (Description and Operation)
Noise is any undesirable sound, usually unpleasant in nature. Vibration is
any motion, shaking or
trembling, that can be felt or seen ...

Noise, Vibration and Harshness (NVH) (Description and Operation)
Noise is any undesirable sound, usually unpleasant in nature. Vibration is
any motion, shaking or
trembling, that can be felt or seen ...

Other materials:

Crankshaft Pulley
Engine
A modular engine is built around four modules:
the intake module
the cylinder head module (RH)
the cylinder head module (LH)
the lower engine module
While not all repairs can take advantage of the modular conc ...

Engine - 4.6L (2V)
General Specifications
a - With installation of a new filter.
b - Distance front edge of bearing is installed below front face of cylinder
block.
c - Time necessary for plunger to leak down 1.6 mm of travel with 222 N force
and leak down fluid in
tap ...

Exhaust System Neutralizing
Noise, Vibration and Harshness (NVH) (Description and Operation)
Noise is any undesirable sound, usually unpleasant in nature. Vibration is
any motion, shaking or
trembling, that can be felt or seen when an object moves back and forth or up
and down. Harshne ...